This application describes examples and embodiments of techniques and systems for laser surgery within the anterior segment of the eye the crystalline lens via photodisruption caused by laser pulses. Various lens surgical procedures for removal of the crystalline lens utilize various techniques to break up the lens into small fragments that can be removed from the eye through small incisions. These procedures use manual instruments, ultrasound, heated fluids or lasers and tend to have significant drawbacks, including the need to enter the eye with probes in order to accomplish the fragmentation, and the limited precision associated with such lens fragmentation techniques.
Photodisruptive laser technology can deliver laser pulses into the lens to optically fragment the lens without insertion of a probe and thus can offer the potential for improved lens removal. Laser-induced photodisruption has been widely used in laser ophthalmic surgery and Nd:YAG lasers have been frequently used as the laser sources, including lens fragmentation via laser induced photodisruption. Some existing systems utilize nanosecond lasers with pulse energies of several mJ (E. H. Ryan et al. American Journal of Opthalmology 104: 382-386, October 1987; R. R. Kruger et al. Opthalmology 108: 2122-2129, 2001), and picosecond lasers with several tens of μJ (A. Gwon et al. J. Cataract Refract Surg. 21, 282-286, 1995). These relatively long pulses deposit relatively large amounts of energy into the surgical spots, resulting in considerable limitations on the precision and control of the procedure, while creating a relatively high level of risk of unwanted outcomes.
In parallel, in the related field of cornea surgery it was recognized that shorter pulse durations and better focusing can be achieved by using pulses of duration of hundreds of femtoseconds instead of the nanosecond and picosecond pulses. Femtosecond pulses deposit much less energy per pulse, significantly increasing the precision and the safety of the procedure.
Presently several companies commercialize femtosecond laser technology for ophthalmic procedures on the cornea, such as LASIK flaps and corneal transplants. These companies include Intralase Corp./Advanced Medical Optics, USA, 20/10 Perfect Vision Optische Geräte GmbH, Germany, Carl Zeiss Meditec, Inc. Germany, and Ziemer Ophthalmic Systems AG, Switzerland.
However, these systems are designed according to the requirements of the cornea surgery. Crucially, the depth range of the laser focus is typically less than about 1 mm, the thickness of the cornea. As such, these designs do not offer solutions for the considerable challenges of performing surgery on the lens of the eye.